The effects caused by alkaline treatment on the susceptibility of waste cardboard to enzymatic hydrolysis have been studied. Optimised conditions leading to extensive saccharification of both cellulose (870g kg(-1) conversion) and hemicelluloses (845g kg(-1) conversion) were identified. Samples treated under selected operational conditions were employed for producing D-lactic acid by simultaneous saccharification and fermentation (SSF) in media containing cellulases, beta-glucosidase and Lactobacillus coryniformis ssp torquens cells. SSF fed-batch experiments led to D-lactic acid concentrations up to 23.4 g dm(-3) at a product yield of 514g lactic acid kg(-1) of potential glucose and a volumetric productivity of 0.48g dm(-3) h(-1). (C) 2004 Society of Chemical Industry.